This invention relates to a composition comprising a purified mycobacterial lipid cell-wall component or analog or derivative thereof and a pharmaceutically acceptable excipient, medium, carrier or adjuvant and the use of the purified mycobacterial lipid cell-wall component or analog or derivative thereof and the composition containing it in the prevention, treatment and diagnosis of disease.
It has been known for a long time that BCG*) vaccination leads to the induction of a positive tuberculin skin test, resulting in delayed type hypersensitivity (DTH). This delayed hypersensitivity in turn has been considered to be indicative of the successful induction of protective immunity against tuberculosis and has led to the almost world-wide BCG immunization in the 1950s-1970s. This convenient test is in fact the only immunological criterion/parameter on which epidemiological assessments of the effectiveness of the immunization have been based.
*) BCG: (Bacillus of Calmette and Guerin) Calmette and Guerin attentuated a strain of M. bovis by passaging it 231 times over a period of 13 years through a medium containing glycerine and ox-bile. 
This view is no longer generally accepted and many immunologists are of the opinion that                i) the induction of DTH is not directly related to the degree of protective immunity;        ii) the protective efficacy obtained in vaccination with BCG varies between 0 to 80% (Snider, 1994)and in addition        iii) BCG vaccination has detrimental side-effects being partially responsible for tissue destruction in patients, without offering sufficient protection (Fine, 1994).        
The unsatisfactory results observed and reported in a number of countries with the BCG vaccine currently used for the prevention of the spread of tuberculosis (Dolin, Raviglione and Koch, 1994; Snider, 1994) could be explained by:                i) variations between BCG vaccines, which could be caused by strain variation or by differences between manufacturing processes;        ii) differences in pathogenesis of Mycobacterium tuberculosis;         iii) differences in the exposure to the environmental mycobacteria. The environmental mycobacteria may act antagonistically or synergistically with BCG;        iv) genetic differences between population groups subjected to vaccination with BCG;        v) differences in nutrition and exposure to sunlight between various population groups;        vi) differences between designs of various studies;        vii) inadequacies of the criteria used for the evaluation of protective effects of vaccination with BCG.        
Efforts directed at finding an effective vaccine capable of inducing long-lasting immunity have centered over the last decade on three main approaches:                i) identifying “protective” antigens and epitopes of M. tuberculosis presented by macrophages and recognized by human lymphocytes;        ii) developing a DNA-based vaccine with protective antigen and interleukin genes (Lowrie et al., 1994);        iii) identifying which types of cells of the immune system and which types of cytokines are involved in tuberculosis in order to manipulate their activity towards offering a cure or protection against tuberculosis.        